In an image forming apparatus such as a printer, a copier, or a facsimile equipment that forms an image using a toner consisting of powder, a magnet roller having a plurality of magnetic poles in a circumferential direction is used in a developing device or a cleaning device. The magnet roller used in the developing device develops an electrostatic latent image formed on a photoconductor drum surface by using a charged toner, and the magnet roller used in the cleaning device removes the charged toner remaining on the photoconductor drum surface.
In regard to the magnet roller, Patent Documents 1, 2, and 3 disclose examples of connecting two semicylindrical resin magnets and forming a cylindrical magnet roller. That is, in all of these examples, the magnet roller constituted of the two semicylindrical resin magnets is provided, and a shaft protruding from both ends is produced by utilizing end portions of the resin magnets.
Connecting the plurality of resin magnets to one independent metal shaft to manufacture the magnet roller has been well-known and, for example, Patent Document 4 discloses that five magnet pieces each having a fan-shaped cross section are attached to a metal shaft to form a magnet roller.
Pressing a metal shaft into an inner hole of a resin magnet extruded into a cylindrical shape to form a magnet roller has been also well-known and, for example, Patent Document 5 discloses that a cored bar is pressed into a cylindrical resin magnet using an elastomer resin like an EEA resin as a binder and a magnet roller is formed.